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Gdk::GC Class Reference

All drawing operations in GDK take a graphics context (GC) argument. More...

Inheritance diagram for Gdk::GC:
[legend]
Collaboration diagram for Gdk::GC:
[legend]

## Public Member Functions
| GC (GC&& src) noexcept
GC& | operator= (GC&& src) noexcept
| ~GC () noexceptoverride
GdkGC* | gobj ()
| Provides access to the underlying C GObject. More...
const GdkGC* | gobj () const
| Provides access to the underlying C GObject. More...
GdkGC* | gobj_copy ()
| Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs. More...
void | set_foreground (const Color& color)
| Sets the foreground color for a graphics context. More...
void | set_background (const Color& color)
| Sets the background color for a graphics context. More...
void | set_function (Function function)
| Determines how the current pixel values and the pixel values being drawn are combined to produce the final pixel values. More...
void | set_fill (Fill fill)
| Set the fill mode for a graphics context. More...
void | set_tile (const Glib::RefPtr< Pixmap >& tile)
| Set a tile pixmap for a graphics context. More...
void | set_stipple (const Glib::RefPtr< Pixmap >& stipple)
| Set the stipple bitmap for a graphics context. More...
void | set_ts_origin (int x, int y)
| Set the origin when using tiles or stipples with the GC. More...
void | set_clip_origin (int x, int y)
| Sets the origin of the clip mask. More...
void | set_clip_mask (const Glib::RefPtr< Bitmap >& mask)
| Sets the clip mask for a graphics context from a bitmap. More...
void | set_clip_rectangle (Rectangle& rectangle)
| Sets the clip mask for a graphics context from a rectangle. More...
void | set_clip_rectangle (const Rectangle& rectangle)
| Sets the clip mask for a graphics context from a rectangle. More...
void | set_clip_region (const Region& region)
| Sets the clip mask for a graphics context from a region structure. More...
void | set_subwindow (SubwindowMode mode)
| Sets how drawing with this GC on a window will affect child windows of that window. More...
void | set_exposures (bool exposures)
| Sets whether copying non-visible portions of a drawable using this graphics context generate exposure events for the corresponding regions of the destination drawable. More...
void | set_line_attributes (int line_width, LineStyle line_style, CapStyle cap_style, JoinStyle join_style)
| Sets various attributes of how lines are drawn. More...
void | set_dashes (int dash_offset, gint8* dash_list, int n)
| Sets the way dashed-lines are drawn. More...
void | offset (int x_offset, int y_offset)
| Offset attributes such as the clip and tile-stipple origins of the GC so that drawing at x - x_offset, y - y_offset with the offset GC has the same effect as drawing at x, y with the original GC. More...
void | set_colormap (const Glib::RefPtr< Colormap >& colormap)
| Sets the colormap for the GC to the given colormap. More...
Glib::RefPtr< Colormap > | get_colormap ()
| Retrieves the colormap for a given GC, if it exists. More...
void | set_rgb_fg_color (const Color& color)
| Set the foreground color of a GC using an unallocated color. More...
void | set_rgb_bg_color (const Color& color)
| Set the background color of a GC using an unallocated color. More...
Glib::RefPtr< Screen > | get_screen ()
| Gets the Gdk::Screen for which gc was created. More...
Glib::RefPtr< const Screen > | get_screen () const
| Gets the Gdk::Screen for which gc was created. More...
Public Member Functions inherited from Glib::Object
| Object (const Object &)=delete
Object & | operator= (const Object &)=delete
| Object (Object &&src) noexcept
Object & | operator= (Object &&src) noexcept
void * | get_data (const QueryQuark &key)
void | set_data (const Quark &key, void *data)
void | set_data (const Quark &key, void *data, DestroyNotify notify)
void | remove_data (const QueryQuark &quark)
void * | steal_data (const QueryQuark &quark)
Glib::RefPtr< Glib::Object > | wrap (GObject *object, bool take_copy=false)
Public Member Functions inherited from Glib::ObjectBase
| ObjectBase (const ObjectBase &)=delete
ObjectBase & | operator= (const ObjectBase &)=delete
void | set_property_value (const Glib::ustring &property_name, const Glib::ValueBase &value)
void | get_property_value (const Glib::ustring &property_name, Glib::ValueBase &value) const
void | set_property (const Glib::ustring &property_name, const PropertyType &value)
void | get_property (const Glib::ustring &property_name, PropertyType &value) const
void | connect_property_changed (const Glib::ustring &property_name, const sigc::slot< void > &slot)
void | connect_property_changed (const Glib::ustring &property_name, sigc::slot< void > &&slot)
sigc::connection | connect_property_changed_with_return (const Glib::ustring &property_name, const sigc::slot< void > &slot)
sigc::connection | connect_property_changed_with_return (const Glib::ustring &property_name, sigc::slot< void > &&slot)
void | freeze_notify ()
void | thaw_notify ()
virtual void | reference () const
virtual void | unreference () const
GObject * | gobj ()
const GObject * | gobj () const
GObject * | gobj_copy () const
Public Member Functions inherited from sigc::trackable
| trackable () noexcept
| trackable (const trackable &src) noexcept
| trackable (trackable &&src)
| ~trackable ()
void | add_destroy_notify_callback (void *data, func_destroy_notify func) const
void | notify_callbacks ()
trackable & | operator= (const trackable &src)
trackable & | operator= (trackable &&src)
void | remove_destroy_notify_callback (void *data) const

## Static Public Member Functions
static GType | get_type ()
| Get the GType for this class, for use with the underlying GObject type system. More...
static Glib::RefPtr< GC > | create ()
static Glib::RefPtr< GC > | create (const Glib::RefPtr< Drawable >& drawable)

## Protected Member Functions
| GC ()
| GC (const Glib::RefPtr< Drawable >& drawable)
Protected Member Functions inherited from Glib::Object
| Object ()
| Object (const Glib::ConstructParams &construct_params)
| Object (GObject *castitem)
| ~Object () noexceptoverride
Protected Member Functions inherited from Glib::ObjectBase
| ObjectBase ()
| ObjectBase (const char *custom_type_name)
| ObjectBase (const std::type_info &custom_type_info)
| ObjectBase (ObjectBase &&src) noexcept
ObjectBase & | operator= (ObjectBase &&src) noexcept
virtual | ~ObjectBase () noexcept=0
void | initialize (GObject *castitem)
void | initialize_move (GObject *castitem, Glib::ObjectBase *previous_wrapper)

## Related Functions
(Note that these are not member functions.)
Glib::RefPtr< Gdk::GC > | wrap (GdkGC* object, bool take_copy=false)
| A Glib::wrap() method for this object. More...

## Additional Inherited Members
Public Types inherited from Glib::Object
typedef void(*)(gpointer data | DestroyNotify)
Public Types inherited from sigc::trackable
typedef internal::func_destroy_notify | func_destroy_notify

## Detailed Description

All drawing operations in GDK take a graphics context (GC) argument.

A graphics context encapsulates information about the way things are drawn, such as the foreground color or line width. By using graphics contexts, the number of arguments to each drawing call is greatly reduced, and communication overhead is minimized, since identical arguments do not need to be passed repeatedly.

## Constructor & Destructor Documentation

Gdk::GC::GC | ( | GC&& | src | ) |
| noexcept

Gdk::GC::~GC | ( |  | ) |
| override noexcept

Gdk::GC::GC | ( |  | ) |
| protected

Gdk::GC::GC | ( | const Glib::RefPtr< Drawable >& | drawable | ) |
| explicit protected

## Member Function Documentation

static Glib::RefPtr<GC> Gdk::GC::create | ( |  | ) |
| static

static Glib::RefPtr<GC> Gdk::GC::create | ( | const Glib::RefPtr< Drawable >& | drawable | ) |
| static

Glib::RefPtr<Colormap> Gdk::GC::get_colormap | ( |  | ) |

Retrieves the colormap for a given GC, if it exists.

A GC will have a colormap if the drawable for which it was created has a colormap, or if a colormap was set explicitely with gdk_gc_set_colormap.

Deprecated: 2.22: There is no replacement. Cairo handles colormaps automatically, so there is no need to care about them.

Returns
  The colormap of gc, or `nullptr` if gc doesn't have one.

Glib::RefPtr<Screen> Gdk::GC::get_screen | ( |  | ) |

Gets the Gdk::Screen for which gc was created.

Since gtkmm 2.2:

Returns
  The Gdk::Screen for gc.

Glib::RefPtr<const Screen> Gdk::GC::get_screen | ( |  | ) | const

Gets the Gdk::Screen for which gc was created.

Since gtkmm 2.2:

Returns
  The Gdk::Screen for gc.

static GType Gdk::GC::get_type | ( |  | ) |
| static

Get the GType for this class, for use with the underlying GObject type system.

GdkGC* Gdk::GC::gobj | ( |  | ) |
| inline

Provides access to the underlying C GObject.

const GdkGC* Gdk::GC::gobj | ( |  | ) | const
| inline

Provides access to the underlying C GObject.

GdkGC* Gdk::GC::gobj_copy | ( |  | ) |

Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs.

void Gdk::GC::offset | ( | int | x_offset,
|  | int | y_offset
| ) |  |

Offset attributes such as the clip and tile-stipple origins of the GC so that drawing at x - x_offset, y - y_offset with the offset GC has the same effect as drawing at x, y with the original GC.

Deprecated: 2.22: There is no direct replacement, as this is just a convenience function for gdk_gc_set_ts_origin and set_clip_origin().

Parameters

  x_offset | Amount by which to offset the GC in the X direction.
  y_offset | Amount by which to offset the GC in the Y direction.

GC& Gdk::GC::operator= | ( | GC&& | src | ) |
| noexcept

void Gdk::GC::set_background | ( | const Color& | color | ) |

Sets the background color for a graphics context.

Note that this function uses color->pixel, use set_rgb_bg_color() to specify the background color as red, green, blue components.

Deprecated: 2.22: Use gdk_cairo_set_source_color() to use a Gdk::Color as the source in Cairo. Note that if you want to draw a background and a foreground in Cairo, you need to call drawing functions (like cairo_fill()) twice.

Parameters

  color | The new background color.

void Gdk::GC::set_clip_mask | ( | const Glib::RefPtr< Bitmap >& | mask | ) |

Sets the clip mask for a graphics context from a bitmap.

The clip mask is interpreted relative to the clip origin. (See set_clip_origin()).

Deprecated: 2.22: Use cairo_mask() instead.

Parameters

  mask | A bitmap.

void Gdk::GC::set_clip_origin | ( | int | x,
|  | int | y
| ) |  |

Sets the origin of the clip mask.

The coordinates are interpreted relative to the upper-left corner of the destination drawable of the current operation.

Deprecated: 2.22: Use cairo_translate() before applying the clip path in Cairo.

Parameters

  x | The x-coordinate of the origin.
  y | The y-coordinate of the origin.

void Gdk::GC::set_clip_rectangle | ( | Rectangle& | rectangle | ) |

Sets the clip mask for a graphics context from a rectangle.

The clip mask is interpreted relative to the clip origin. (See set_clip_origin()).

Deprecated: 2.22: Use cairo_rectangle() and cairo_clip() in Cairo.

Deprecated:
  Use set_clip_rectangle(const Rectangle& rectangle) instead.

Parameters

  rectangle | The rectangle to clip to.

void Gdk::GC::set_clip_rectangle | ( | const Rectangle& | rectangle | ) |

Sets the clip mask for a graphics context from a rectangle.

The clip mask is interpreted relative to the clip origin. (See set_clip_origin()).

Deprecated: 2.22: Use cairo_rectangle() and cairo_clip() in Cairo.

Parameters

  rectangle | The rectangle to clip to.

void Gdk::GC::set_clip_region | ( | const Region& | region | ) |

Sets the clip mask for a graphics context from a region structure.

The clip mask is interpreted relative to the clip origin. (See set_clip_origin()).

Deprecated: 2.22: Use gdk_cairo_region() and cairo_clip() in Cairo.

Parameters

  region | The Gdk::Region.

void Gdk::GC::set_colormap | ( | const Glib::RefPtr< Colormap >& | colormap | ) |

Sets the colormap for the GC to the given colormap.

The depth of the colormap's visual must match the depth of the drawable for which the GC was created.

Deprecated: 2.22: There is no replacement. Cairo handles colormaps automatically, so there is no need to care about them.

Parameters

  colormap | A Gdk::Colormap.

void Gdk::GC::set_dashes | ( | int | dash_offset,
|  | gint8 * | dash_list,
|  | int | n
| ) |  |

Sets the way dashed-lines are drawn.

Lines will be drawn with alternating on and off segments of the lengths specified in dash_list. The manner in which the on and off segments are drawn is determined by the line_style value of the GC. (This can be changed with set_line_attributes().)

The dash_offset defines the phase of the pattern, specifying how many pixels into the dash-list the pattern should actually begin.

Deprecated: 2.22: Use cairo_set_dash() to set the dash in Cairo.

Parameters

  dash_offset | The phase of the dash pattern.
  dash_list | An array of dash lengths.
  n | The number of elements in dash_list.

void Gdk::GC::set_exposures | ( | bool | exposures | ) |

Sets whether copying non-visible portions of a drawable using this graphics context generate exposure events for the corresponding regions of the destination drawable.

(See gdk_draw_drawable()).

Deprecated: 2.22: There is no replacement. If you need to control exposures, you must use drawing operations of the underlying window system or use Gdk::Window::invalidate_rect(). Cairo will never generate exposures.

Parameters

  exposures | If `true`, exposure events will be generated.

void Gdk::GC::set_fill | ( | Fill | fill | ) |

Set the fill mode for a graphics context.

Deprecated: 2.22: You can achieve tiling in Cairo by using cairo_pattern_set_extend() on the source. For stippling, see the deprecation comments on set_stipple().

Parameters

  fill | The new fill mode.

void Gdk::GC::set_foreground | ( | const Color& | color | ) |

Sets the foreground color for a graphics context.

Note that this function uses color->pixel, use set_rgb_fg_color() to specify the foreground color as red, green, blue components.

Deprecated: 2.22: Use gdk_cairo_set_source_color() to use a Gdk::Color as the source in Cairo.

Parameters

  color | The new foreground color.

void Gdk::GC::set_function | ( | Function | function | ) |

Determines how the current pixel values and the pixel values being drawn are combined to produce the final pixel values.

Deprecated: 2.22: Use cairo_set_operator() with Cairo.

Parameters

  function | The Gdk::Function to use.

void Gdk::GC::set_line_attributes | ( | int | line_width,
|  | LineStyle | line_style,
|  | CapStyle | cap_style,
|  | JoinStyle | join_style
| ) |  |

Sets various attributes of how lines are drawn.

See the corresponding members of Gdk::GCValues for full explanations of the arguments.

Deprecated: 2.22: Use the Cairo functions cairo_set_line_width(), cairo_set_line_join(), cairo_set_line_cap() and cairo_set_dash() to affect the stroking behavior in Cairo. Keep in mind that the default attributes of a #cairo_t are different from the default attributes of a Gdk::GC.

Parameters

  line_width | The width of lines.
  line_style | The dash-style for lines.
  cap_style | The manner in which the ends of lines are drawn.
  join_style | The in which lines are joined together.

void Gdk::GC::set_rgb_bg_color | ( | const Color& | color | ) |

Set the background color of a GC using an unallocated color.

The pixel value for the color will be determined using GdkRGB. If the colormap for the GC has not previously been initialized for GdkRGB, then for pseudo-color colormaps (colormaps with a small modifiable number of colors), a colorcube will be allocated in the colormap.

Calling this function for a GC without a colormap is an error.

Deprecated: 2.22: Use gdk_cairo_set_source_color() instead.

Parameters

  color | An unallocated Gdk::Color.

void Gdk::GC::set_rgb_fg_color | ( | const Color& | color | ) |

Set the foreground color of a GC using an unallocated color.

The pixel value for the color will be determined using GdkRGB. If the colormap for the GC has not previously been initialized for GdkRGB, then for pseudo-color colormaps (colormaps with a small modifiable number of colors), a colorcube will be allocated in the colormap.

Calling this function for a GC without a colormap is an error.

Deprecated: 2.22: Use gdk_cairo_set_source_color() instead.

Parameters

  color | An unallocated Gdk::Color.

void Gdk::GC::set_stipple | ( | const Glib::RefPtr< Pixmap >& | stipple | ) |

Set the stipple bitmap for a graphics context.

The stipple will only be used if the fill mode is Gdk::STIPPLED or Gdk::OPAQUE_STIPPLED.

Deprecated: 2.22: Stippling has no direct replacement in Cairo. If you want to achieve an identical look, you can use the stipple bitmap as a mask. Most likely, this involves rendering the source to an intermediate surface using cairo_push_group() first, so that you can then use cairo_mask() to achieve the stippled look.

Parameters

  stipple | The new stipple bitmap.

void Gdk::GC::set_subwindow | ( | SubwindowMode | mode | ) |

Sets how drawing with this GC on a window will affect child windows of that window.

Deprecated: 2.22: There is no replacement. If you need to control subwindows, you must use drawing operations of the underlying window system manually. Cairo will always use Gdk::INCLUDE_INFERIORS on sources and masks and Gdk::CLIP_BY_CHILDREN on targets.

Parameters

  mode | The subwindow mode.

void Gdk::GC::set_tile | ( | const Glib::RefPtr< Pixmap >& | tile | ) |

Set a tile pixmap for a graphics context.

This will only be used if the fill mode is Gdk::TILED.

Deprecated: 2.22: The following code snippet sets a tiling Gdk::Pixmap as the source in Cairo:

[C example ellipted]

Parameters

  tile | The new tile pixmap.

void Gdk::GC::set_ts_origin | ( | int | x,
|  | int | y
| ) |  |

Set the origin when using tiles or stipples with the GC.

The tile or stipple will be aligned such that the upper left corner of the tile or stipple will coincide with this point.

Deprecated: 2.22: You can set the origin for tiles and stipples in Cairo by changing the source's matrix using cairo_pattern_set_matrix(). Or you can specify it with gdk_cairo_set_source_pixmap() as shown in the example for set_tile().

Parameters

  x | The x-coordinate of the origin.
  y | The y-coordinate of the origin.

## Friends And Related Function Documentation

Glib::RefPtr< Gdk::GC > wrap | ( | GdkGC * | object,
|  | bool | take_copy = `false`
| ) |  |
| related

A Glib::wrap() method for this object.

Parameters

  object | The C instance.
  take_copy | False if the result should take ownership of the C instance. True if it should take a new copy or ref.

Returns
  A C++ instance that wraps this C instance.

The documentation for this class was generated from the following file:

- gdkmm/gc.h